本文实例讲述了Android测量每秒帧数Frames Per Second (FPS)的方法。分享给大家供大家参考。具体如下：
MainThread.java：
package net.obviam.droidz; import java.text.DecimalFormat; import android.graphics.Canvas; import android.util.Log; import android.view.SurfaceHolder; /** * @author impaler * * The Main thread which contains the game loop. The thread must have access to * the surface view and holder to trigger events every game tick. */ public class MainThread extends Thread { private static final String TAG = MainThread.class.getSimpleName(); // desired fps private final static int MAX_FPS = 50; // maximum number of frames to be skipped private final static int MAX_FRAME_SKIPS = 5; // the frame period private final static int FRAME_PERIOD = 1000 / MAX_FPS; // Stuff for stats */ private DecimalFormat df = new DecimalFormat("0.##"); // 2 dp // we'll be reading the stats every second private final static int STAT_INTERVAL = 1000; //ms // the average will be calculated by storing // the last n FPSs private final static int FPS_HISTORY_NR = 10; // last time the status was stored private long lastStatusStore = 0; // the status time counter private long statusIntervalTimer = 0l; // number of frames skipped since the game started private long totalFramesSkipped = 0l; // number of frames skipped in a store cycle (1 sec) private long framesSkippedPerStatCycle = 0l; // number of rendered frames in an interval private int frameCountPerStatCycle = 0; private long totalFrameCount = 0l; // the last FPS values private double fpsStore[]; // the number of times the stat has been read private long statsCount = 0; // the average FPS since the game started private double averageFps = 0.0; // Surface holder that can access the physical surface private SurfaceHolder surfaceHolder; // The actual view that handles inputs // and draws to the surface private MainGamePanel gamePanel; // flag to hold game state private boolean running; public void setRunning(boolean running) { this.running = running; } public MainThread(SurfaceHolder surfaceHolder, MainGamePanel gamePanel) { super(); this.surfaceHolder = surfaceHolder; this.gamePanel = gamePanel; } @Override public void run() { Canvas canvas; Log.d(TAG, "Starting game loop"); // initialise timing elements for stat gathering initTimingElements(); long beginTime; // the time when the cycle begun long timeDiff; // the time it took for the cycle to execute int sleepTime; // ms to sleep (<0 if we're behind) int framesSkipped; // number of frames being skipped sleepTime = 0; while (running) { canvas = null; // try locking the canvas for exclusive pixel editing // in the surface try { canvas = this.surfaceHolder.lockCanvas(); synchronized (surfaceHolder) { beginTime = System.currentTimeMillis(); framesSkipped = 0; // resetting the frames skipped // update game state this.gamePanel.update(); // render state to the screen // draws the canvas on the panel this.gamePanel.render(canvas); // calculate how long did the cycle take timeDiff = System.currentTimeMillis() - beginTime; // calculate sleep time sleepTime = (int)(FRAME_PERIOD - timeDiff); if (sleepTime > 0) { // if sleepTime > 0 we're OK try { // send the thread to sleep for a short period // very useful for battery saving Thread.sleep(sleepTime); } catch (InterruptedException e) {} } while (sleepTime < 0 && framesSkipped < MAX_FRAME_SKIPS) { // we need to catch up this.gamePanel.update(); // update without rendering sleepTime += FRAME_PERIOD; // add frame period to check if in next frame framesSkipped++; } if (framesSkipped > 0) { Log.d(TAG, "Skipped:" + framesSkipped); } // for statistics framesSkippedPerStatCycle += framesSkipped; // calling the routine to store the gathered statistics storeStats(); } } finally { // in case of an exception the surface is not left in // an inconsistent state if (canvas != null) { surfaceHolder.unlockCanvasAndPost(canvas); } } // end finally } } /** * The statistics - it is called every cycle, it checks if time since last * store is greater than the statistics gathering period (1 sec) and if so * it calculates the FPS for the last period and stores it. * * It tracks the number of frames per period. The number of frames since * the start of the period are summed up and the calculation takes part * only if the next period and the frame count is reset to 0. */ private void storeStats() { frameCountPerStatCycle++; totalFrameCount++; // check the actual time statusIntervalTimer += (System.currentTimeMillis() - statusIntervalTimer); if (statusIntervalTimer >= lastStatusStore + STAT_INTERVAL) { // calculate the actual frames pers status check interval double actualFps = (double)(frameCountPerStatCycle / (STAT_INTERVAL / 1000)); //stores the latest fps in the array fpsStore[(int) statsCount % FPS_HISTORY_NR] = actualFps; // increase the number of times statistics was calculated statsCount++; double totalFps = 0.0; // sum up the stored fps values for (int i = 0; i < FPS_HISTORY_NR; i++) { totalFps += fpsStore[i]; } // obtain the average if (statsCount < FPS_HISTORY_NR) { // in case of the first 10 triggers averageFps = totalFps / statsCount; } else { averageFps = totalFps / FPS_HISTORY_NR; } // saving the number of total frames skipped totalFramesSkipped += framesSkippedPerStatCycle; // resetting the counters after a status record (1 sec) framesSkippedPerStatCycle = 0; statusIntervalTimer = 0; frameCountPerStatCycle = 0; statusIntervalTimer = System.currentTimeMillis(); lastStatusStore = statusIntervalTimer; // Log.d(TAG, "Average FPS:" + df.format(averageFps)); gamePanel.setAvgFps("FPS: " + df.format(averageFps)); } } private void initTimingElements() { // initialise timing elements fpsStore = new double[FPS_HISTORY_NR]; for (int i = 0; i < FPS_HISTORY_NR; i++) { fpsStore[i] = 0.0; } Log.d(TAG + ".initTimingElements()", "Timing elements for stats initialised"); } }
希望本文所述对大家的java程序设计有所帮助。